Solar power tower system

ABSTRACT

A solar power tower system includes a solar tower receiver, a cold storage tank and a hot storage tank at the bottom of the tower receiver with a heat transfer fluid down pipe from the receiver and a working fluid up pipe into the receiver. A potential energy recovery system is located at the bottom of the tower configured such that it recovers part of the mechanical energy of the heat transfer fluid and uses it in the pumping of the working fluid to the receiver and providing power to other equipment in the solar power tower system in any kind of energy.

TECHNICAL FIELD

This invention is related to power generation systems through the solarenergy. Specifically, the invention is applied to solar power towerplants, with cylindrical central receiver configuration or with thecavity receptor configuration.

BACKGROUND

The growing interest in renewable energies and the increase of theenergy demand has produced a strong expansion in the solar electricgeneration.

The central receiver concept is based on a field of individuallysun-tracking mirrors called heliostats, which reflect the incident solarradiation to a receiver at the top of a centrally located tower (thereceiver could be cylindrical or with cavity configuration). This way,the direct radiation is concentrated in the effective area of thereceiver allowing it to reach high levels of radiation.

Any of the receiver configurations is usually positioned at the top ofthe tower, where it is heated by the reflected radiation fromheliostats. The heliostats concentrate and redirect the sun radiationtowards the receiver. Typically 80 to 90 percent of the reflected energyis absorbed and transferred to the working fluid, which is pumped up thetower and is also pumped into the receiver. Solar power tower systemsusually include a “cold” storage tank and a “hot” storage tank at thebottom of the tower, which provide and collect the fluid that goesthrough the receiver. This technology also has an energy conversionsystem, composed of a steam generator and a turbine/generator set.

The heat transfer fluid can be any medium that has the ability to absorband transfer the energy as heat properly, such molten salts orhigh-temperature synthetic thermal oils under 750° C.

The heat transfer fluid is pumped from the cold tank to the top of thetower, where it circulates inside the receiver. In the receiver outlet,the heat transfer fluid has high mechanical energy, sum of its kineticenergy (originated by the velocity produced by the pumps) and of itspotential energy (as a result of its high height at the top of thetower).

The working fluid is introduced in the hot tank after being introducedthrough the tower. Due to the high kinetic energy in the inlet, it isnecessary to dissipate an important part of the energy to avoid problemsand possible damages of performance in the tank storage system. For thisreason, a system of plates that produces the necessary pressure drop toeliminate the high energy in the pipe has been traditionally employed.

The quantity of energy dissipated in the system of pressure drop is animportant value which is not recovered. The invention developed in thisdocument shows several alternatives that can recover around the 70percent of the energy previously dissipated and wasted.

At the same time, this recovered energy can be employed in the pumpingof the fluid to the receiver. This way, the auto-consumption of theplant will be reduced, by improving the performance and the benefits ofthe plant.

The approach of this invention and its utility have been developed afterhaving a high understanding and knowledge of the operation of towerpower plants.

SUMMARY

This invention refers to a solar power tower system which comprises asolar tower receiver, a “cold” storage tank and a “hot” storage tank atthe bottom of the tower receiver, which recovers part of the mechanicalenergy of the heat transfer fluid and then it uses this recovered energyin the pumping of the working fluid to the receiver by potential energyrecovery system.

The potential energy recovery system have parallel configuration againstthe solar power tower and the cold and hot tanks, so that it lets thesystem to couple or uncouple the solar power tower system operation atany moment, in case of damage of the system or low process profitabilityunder certain circumstances

On the one hand, for the generic operation of the solar power towersystem, a plurality of valves communicate the potential energy recoverysystem with the rest of the circuit and will be closed, by connectingthe potential energy recovery system and closing the complete circuit.On the other hand, when the use of potential energy recovery system isnot advantageous, the valves will be opened and the potential energyrecovery system will be isolated, so the plant will work as it doesnowadays.

The solar power tower system can comprise a plurality of potentialenergy recovery systems operating in parallel.

The potential energy recovery system, is located at the bottom of thetower attached to the hot flow drop pipe and could be located betweenthe receiver and the hot tank, and also between the receiver and thecold tank in more complex configurations. The thermal fluid thatcirculates through the receiver is located in the most elevated part ofthe tower, providing a certain potential energy.

The aim of the potential energy recovery system is to recover all thepossible potential energy from the heat transfer fluid.

The potential energy recovery system could comprise:

-   -   at least one axial or radial turbine or at least a piston that        recover potential energy from a fluid to another,

Additionally it can comprise:

-   -   at least one pump that will propel the cold tank thermal flow to        the receiver.

In this case, the pump is mechanically joined by clutch and gears to aturbine and shall be located relatively close to each other to avoidusing excessively complex mechanical transmission systems. A perfectlocation to perform this mechanical joint or any other might be locatedwhere the pipes of hot and cold thermal fluid are divided from eachother at the bottom of the tower.

The potential energy recovery system positioning shall be at the bottomof the tower trying to obtain the most potential energy as possible.This place may be located in a previous point to the discharge of thehot fluid coming from the tower in a tank.

In case of an electric/magnetic joint, the potential energy recoverysystem could comprise an electric generator able to transmit thegenerated mechanical energy from the at least one turbine or at leastone piston, to any other component in the solar power tower system.

In case of a fluid dynamic operation, the potential energy recoverysystem will comprise a plurality of pistons located between the downpipe and up pipe configured such that the heat transfer fluid from thedown pipe (hot pipe) moves the pistons directly transferring its energyto the working fluid (cold pipe) which entries into the receiver. Inthis case the distance between de hot pipe and the cold pipe will not bea problem because the potential energy recovery system could compriseauxiliary pipes that communicate with them through auxiliary pipes.

The aim of the potential energy recovery system is to reduce theauto-consumption of the plant with the recovery of potential energy fromthe thermal fluid due to the great height differences that exist in thiskind of technology. Thus, the central efficiency will be higher as aresult of the lower consumption of the components. In addition, in casethe mechanical joints with the pumps impel the cold tank fluid to thetower, the pumps requirements will decrease and they can be able tooperate under lower-demand regimes, this way increasing its lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features are attained andcan be understood in detail, a more detailed description, which isbriefly summarized above, is described below with reference to theFigures illustrated in the appended drawings.

It is to be noted that the Figures in the appended drawings, like thedetailed description, are examples. And as such, the Figures and thedetailed description are not to be considered limiting, and otherequally effective examples are possible and likely. Furthermore, likereference numerals in the Figures indicate like elements: wherein:

FIG. 1 is a block diagram depicting an example of a solar power towersystem with a potential energy recovery system comprising a turbine anda pump.

FIG. 2 is a block diagram depicting an example of a solar power towersystem with a potential energy recovery system comprising a turbine andan electric generator

FIG. 3 is a block diagram depicting an example of a solar power towersystem with a potential energy recovery system comprising a plurality ofpistons.

DETAILED DESCRIPTION

In the following detailed description, the embodiments disclosed are forexemplary purposes only and other embodiments may be employed in lieu ofor in combination with of the embodiments disclosed

EXAMPLE 1

FIG. 1 shows a solar power tower system in which the potential energyrecovery system is a turbine 1 situated at the bottom of the pipe down6. This way, the fluid is conducted through an axial or radial turbine1, extracting the mechanical energy and transforming it in mechanicalenergy in the shaft of the turbine 1. Pressurized fluid ejected throughthe turbine blades leaving it with diminished energy. At the same time,this energy will be transmitted through an axis connected to the shaft apump 2 (could be more than one) that pumps the cold tank into thereceiver.

Furthermore, the transmission shaft will have a clutch 3 which allowsthe system to couple and uncouple, guaranteeing the correct operation inparallel. It would also have a gear box which can be adapted to theneeds.

EXAMPLE 2

FIG. 2 shows another embodiment of the invention in which the potentialenergy recovery system comprises:

-   -   an axial or radial turbine 1 connected to the pipe down 6 which        extracts the energy contained in the fluid, transforming it in        mechanical energy at the exit of the shaft of the turbine 1.    -   an electric generator 4 which transfer the energy from the        turbine through a shaft which communicates them.

The generator will produce electricity that can be employed to cover theauto consumption of the several elements 8 that comprise the solarthermal power tower system. It is preferable used as feeding of the pumpby sending heat transfer fluid to the top. This way, less loss isobtained due to less transmission losses.

Optionally, the correct disposition of the elements that compose thisconfiguration will allow inverting the habitual process of operating.This system that, in emergency situations, if any pump fails, thegenerator could be transformed in motor, producing the necessarymechanical energy to pump from the axial or radial turbine (transformedin motor) feeding the pipe up to the tower.

The continuous line of FIG. 2 shows the operation of the systemgenerating electricity. This electricity can be injected to the pumps 9that feed the receiver or any other component feeding with electricity.

The discontinuous line of FIG. 2 shows the other option discussed above,in which the system is inverted and the turbine 1 and the generator 4are transformed in pump and motor respectively, allowing the receiver tobe fed in emergency situations.

EXAMPLE 3

FIG. 3 shows another embodiment of the invention in which the potentialenergy recovery system, which transforms the mechanical energy of thefluid at the outlet of the tower in useful energy for the pumping intothe receiver, are a plurality of tubes, valves and pistons 5 configuredin order to communicate the two pipes 6, 7 of the tower so that isdirectly the hot fluid the one which transfers its energy to the coldfluid which entries to the tower receiver.

This way, through the natural tendency to equalize the pressure at bothsides of the pistons, the cold fluid will be pumped into the receiverbecause of the high pressure of the hot fluid at the exit of the tower.For example, in the simplest configuration, both fluids must be in thesame tube, only separated by a piston, which will equilibrate thepressures.

To guarantee the continuity in the pumping, it will be necessary to getsome parallel systems, which produce a uniform flow.

1. A solar power tower system comprising: a solar tower receiver; a coldstorage tank and a hot storage tank at the bottom of the tower receiverwith a heat transfer fluid down pipe from the receiver and a workingfluid up pipe into the receiver; a potential energy recovery systemlocated at the bottom of the tower configured such that the potentialenergy recovery system recovers part of the mechanical energy of theheat transfer fluid and uses energy recovered in pumping of workingfluid to the receiver or providing power to other equipment in the solarpower tower system.
 2. The solar power tower system according to claim1, wherein the potential energy recovery system comprises: an axial orradial turbine configured to be activated by heat transfer fluid downfrom the receiver, a pump mechanically joined by a clutch and gears tothe turbine configured to pump the working fluid up into the receiver.3. The solar power tower system according to claim 1, wherein thepotential energy recovery system comprises: an axial or radial turbineconfigured to be activated by heat transfer fluid down from thereceiver, a pump mechanically joined by a clutch and gears to theturbine configured to pump the working fluid up into the receiver, aclutch configured to allow the system to couple and uncouple,guaranteeing correct operation in parallel.
 4. The solar power towersystem according to claim 1, wherein the potential energy recoverysystem comprises: an axial or radial turbine configured to be activatedby the by heat transfer fluid down from the receiver, an electricgenerator and configured to produce connected to the turbine through ashaft.
 5. The solar power tower system according to claim 1, wherein thepotential energy recovery system comprises: a piston configured to beactivated by heat transfer fluid down from the receiver, a pumpmechanically joined by a clutch and gears to the turbine configured topump the working fluid up into the receiver.
 6. The solar power towersystem according to claim 1, wherein the potential energy recoverysystem comprises: a piston configured to be activated by heat transferfluid down from the receiver, a pump mechanically joined by a clutch andgears to the turbine configured to pump the working fluid up into thereceiver. a clutch configured to allow the system to couple anduncouple, guaranteeing correct operation in parallel.
 7. The solar powertower system according to claim 1, wherein the potential energy recoverysystem comprises: a piston configured to be activated by the heattransfer fluid down from the receiver, an electric generator andconfigured to produce electricity connected to the turbine through ashaft.
 8. The solar power tower system according to claim 1, wherein thepotential energy recovery system comprises a plurality of pistonslocated between the down pipe and up pipe configured such that the heattransfer fluid from the down pipe moves the pistons directlytransferring its energy to the working fluid which enters into thereceiver.
 9. The solar power tower system according to claim 1, whereinthe potential energy recovery system is a reversible system.